Conventionally, a configuration has been employed in which a spiral endless conveyor is disposed in a freezer and freezing processing is executed on food and the like being conveyed by the spiral endless conveyor, as a configuration of executing processing such as heating, drying, and freezing on food. The spiral endless conveyor provides an advantage of achieving a smaller conveyor installation area and achieving labor saving by reducing an operation of putting and taking a product to be frozen into and out of the freezer. Patent Document 1 discloses an example of such a conveyor device which is schematically described below with reference to FIG. 21.
In FIG. 21, a spiral endless conveyor device 200 has a spiral endless conveyor belt 204 disposed in a vertical direction in an area surrounded by a plurality of columns 202. An electric motor 206 is disposed in an area around an inlet of the spiral endless conveyor 204 and an auxiliary transmission device 208 is disposed in an interior area of the spiral endless conveyor belt 204. The electric motor 206 drivingly rotates the auxiliary transmission device 208 via a gear 210. A plurality of columns 212, forming the auxiliary transmission device 208, rotate to apply moving force to the spiral endless conveyor belt 204.
The spiral endless conveyor belt 204 includes an inlet path 204A, a spiral ascending path 204B disposed in an interior area of the columns 202, a turning back path 204C disposed at the upper most portion, a spiral descending path 204D, and an outlet path 204E. The upper most portion of the spiral ascending path 204B is connected to the upper most portion of the spiral descending path 204D via the turning back path 204C. The turning back path 204C does not involve reversing of the conveyance surface, and turns back with the same conveyance surface always facing upward. The spiral ascending path 204B and the spiral descending path 204D are alternately arranged in the vertical direction and move in opposite directions.
Patent Document 2 and Patent Document 3 disclose a configuration of a conveyor belt forming a conveyor device. In FIG. 6 in Patent Document 2, a configuration is disclosed which includes tooth-shaped portions, of an involute form, arranged at an equal interval at an outer side portion of the conveyor belt and a toothed wheel which meshes with the tooth-shaped portions, and which drives the conveyor belt with the toothed wheel.
Patent Document 3 discloses a configuration in which supported portions, with a U-shaped cross section opening in the horizontal direction, are disposed at both side portions of the conveyor belt and a guide rail loosely fitted to the supported portions is provided, and the guide rail movably supports the conveyor belt. Patent Document 2 and 3 disclose a configuration in which an anti-drop plate, which prevents a conveyed product from dropping, protrudes upward from a conveyor belt conveyance surface and is fixedly fitted to two adjacent bars forming the conveyor belt.